Fig. 1. The Hubble Deep Field (HDF) as colour composite. It is the deepest high-resolution image ever, containing about 1500 galaxies and reaching down to 30^th magnitude.

The images were taken with the filters^* F450W, F606W, F814W [≅I] (∼35 h each) and F300W (∼50 h) in Cycle 5 [precisely images were taken 18-30 December 1995, using 10 days ≈ 150 orbits] with the Wide Field and Planetary Camera 2 (WFPC2) on board the Hubble Space Telescope (HST).

This part of the HDF project was pointed at a field in the northern continuous viewing zone (CVZ), at α = 12^h 36^m 49.4000^s and δ = +62° 12' 58.000" (J2000 Equinox).
The position was chosen by the following criteria:

• The HDF is several degrees away from any bright star (> 2° from stars < 2 mag);
• The field is devoid of bright nearby galaxies, stars, known nearby clusters, and bright radio sources;
• The field has low infrared cirrus flux, as judged from IRAS maps (as seen here with ``1'' indicating the HDF position),
• low extinction (E_B-V = 0.00 mag),
• low hydrogen column density (log(N_H) = 20.24).

Additionally a 'similar' field in the southern CVZ is planned in the future

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^* The numbers in the filter names indicate central wavelengths of the passbands in nm, W means wide, i.e. broad-band photometry. The broad-band (Δλ ≥ 50 nm) filters in the standard Johnson-Cousins system have not perfect equivalents in the HST filter systems, e.g.:

Fig. 2. The position of the HDF is outlined on this Digitized Sky Survey image.

One clearly sees that the field of view of the WFPC2 is divided into four cameras by a four-faceted pyramid mirror near the HST focal plane. Each of the four cameras (named PC1 [yellow], WF2 [red], WF3 [green], and WF4 [blue]; see text below) contains an 800 × 800 pix² Loral CCD detector. Three of them (named ``Wide Field Camera'' - WFC) operate at an image scale of 0.1"/pix (i.e. 1600 pix ≅ 2' 40" [minus overlap]), the fourth (``Planetary Camera'' - PC) operates at 0.046"/pix (resulting in 34" × 34")